. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. LARVAL SKELETONS AND ORIENTATION 125 B. Figure 2. Live four-armed echinoplutei of Colobocentrotus airattix: (A) oral and (B) lateral views of recently decalcified plutei, (C) ventral view of normal control larva of same age as larvae in A and B, (D) oral view of larva that had been decalcified several days previously and did not regrow a skeleton, (E) and (F) oral views of plutei that had been decalcified several days previously and did regrow a skeleton. lengths and in odd directions, and their body skeletons were equally a
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. LARVAL SKELETONS AND ORIENTATION 125 B. Figure 2. Live four-armed echinoplutei of Colobocentrotus airattix: (A) oral and (B) lateral views of recently decalcified plutei, (C) ventral view of normal control larva of same age as larvae in A and B, (D) oral view of larva that had been decalcified several days previously and did not regrow a skeleton, (E) and (F) oral views of plutei that had been decalcified several days previously and did regrow a skeleton. lengths and in odd directions, and their body skeletons were equally abnormal. Most developed four arms, the correct number, though some had missing or extra arms. In C. atratus and T. gratilla, the postoral arm rods were usually fenestrated as in normal control larvae. No decal- cified larvae developed to six-armed or later stages, but conditions in 20-ml culture dishes were not favorable. Skeletons in echinoplutei appeared to play a small role in immediate mechanical support and a greater role in long-term maintenance and development of larval form. Passive orientation. In still seawater, almost all four- armed echinoplutei of T. gratilla with and without skele- tons oriented passively with their arms upward. Nearly 100% of dead larvae with skeletons sank with arms up- ward, and about 80% of those without skeletons sank with arms upward. However, removal of the skeleton did change the stability in the arms upward orientation. In a cuvette with 100% seawater and side illumination, there were convection currents and velocity gradients; dead echinoplutei with skeletons were oriented arms upward, but dead echinoplutei without skeletons tumbled. Of lar- vae at mid-depth in the ascending current, 100% of those with skeletons were arms-upward (n = 30) and only 28% of those without skeletons were arms-upward with the remainder arms-downward or horizontal (n = 40). We expected that with random orientation about 25% of lar- vae should have been arms upwa
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
